Soy protein concentrate having high isoflavone content and process for its manufacture

ABSTRACT

A method for manufacturing a soy protein concentrate having a low non-digestible oligosaccharide and high isoflavone content. The soy protein may have high saponin content. The method includes the use of a membrane in an ultrafiltration process to separate non-digestible oligosaccharides from protein, while retaining isoflavones and saponins with protein. The soy protein concentrate with a low non-digestible oligosaccharide and high isoflavone and saponin content is useful as a milk substitute and in drink mixes as well as an ingredient in other nutrition and health products.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit under Title 35, U.S.C. §119(e) of U.S. Provisional Patent Application Serial No. 60/282,520,entitled LOW OLIGOSACCHARIDE SOY PROTEIN CONCENTRATE AND PROCESS FOR ITSMANUFACTURE, filed on Apr. 9, 2001.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to a soy protein concentrate that hasdesirable flavor, functional and nutritional properties.

[0004] 2. Description of the Related Art

[0005] The benefits of soy protein are well documented. Cholesterol is amajor concern with consumers throughout the industrialized world. It iswell known that vegetable products contain no cholesterol. For decades,nutritional studies have indicated that the inclusion of soy protein inthe diet actually reduces serum cholesterol levels in people who are atrisk. The higher the cholesterol, the more effective soy proteins are inlowering that level.

[0006] Soybeans have the highest protein content of all cereals andlegumes. In particular, soybeans have about 40% protein, while otherlegumes have 20-30%, and cereals have about 8-15% protein. Soybeans alsocontain about 20% oil with the remaining dry matter mostly carbohydrate(35%). On a wet basis (as is), soybeans contain about 35% protein, 17%oil, 31% carbohydrates, and 4.4% ash.

[0007] In the soybean, both storage protein and lipid bodies arecontained in the usable meat of the soybean (called the cotyledon). Thecomplex carbohydrate (or dietary fiber) is also contained in the cellwalls of the cotyledon. The outer layer of cells (called the seed coat)makes up about 8% of the soybean's total weight. The raw, dehulledsoybean is, depending on the variety, approximately 18% oil, 15% solublecarbohydrates, 15% insoluble carbohydrates, 14% moisture and ash, and38% protein.

[0008] In processing, soybeans are carefully selected for color andsize. The soybeans are then cleaned, conditioned (to make removal of thehull easier) and cracked, dehulled and rolled into flakes. The flakesare subjected to a solvent bath that removes the oil. The solvent isremoved and the flakes are dried, creating the defatted soy flakes thatare the basis of all soy protein products. Despite the large number ofproducts on the market, there are only three types of soy proteinproducts: flours, concentrates and isolates.

[0009] Soy flours are high in oligosaccharides and have a “beany” flavorthat may be objectionable to some consumers. The lack of optimizedprocessing makes soy flours highly variable in terms of quality.

[0010] Soy flours and grits are still widely produced and are used mostoften in baked goods, snack foods and pet foods applications where thehigh flavor profile does not pose a problem. Textured soy flours were anearly attempt at simulating or enhancing the texture of meat products.Texturizing does not change the composition of soy flours and reducesthe flavor profile only slightly. Their primary applications areinexpensive meat products or pet foods.

[0011] The oligosaccharides, raffinose and stachyose, in soy flourpotentially cause flatulence as their bacterial fermentation in thecolon creates intestinal gas. Suarez reported that ingestion of 34 grams(g) of conventional soy flour (1.3 g raffinose and stachyose) caused nosignificant increase in flatulence frequency, whereas ingestion of 80 gof conventional soy flour (3.1 g raffinose and stachyose) resulted in asignificant increase in flatulence frequency. Surarez, Fabrizis L. etal., Am. J. Clin. Nutr., 69:135-9 (1999).

[0012] Soy concentrates have at least 65% protein. A myriad ofapplications have been developed for soy concentrates and texturizedconcentrates in processed foods, meat, poultry, fish, cereal and dairysystems. Soy protein concentrates are made by removing solublecarbohydrate material from defatted soy meal. The most common means forcarbohydrate removal is aqueous alcohol extraction (60-80% ethanol) oracid leaching (isoelectric pH 4.5). In both aqueous alcohol extractionand acid leaching, however, essentially all of the protein is renderedinsoluble. Protein solubility may be recovered in acid leach products byneutralization.

[0013] Isolates are produced through standard chemical isolation,drawing the protein out of the defatted flake through solubilization(alkali extraction at pH 7-10) and separation followed by isoelectricprecipitation. As a result, isolates are 90% protein on a moisture-freebasis. They contain no dietary fiber and are sometimes high in sodium,properties that can limit their application. Their major applicationshave been in dairy substitution, as in infant formulas and milkreplacers.

[0014] It is known that a soy protein product having a substantiallybland taste and colorless appearance may be produced by filtration usinga membrane having a molecular weight cut off (MWCO) of 70,000.

[0015] In recent years, researches have been conducted to betterunderstand the role of isoflavones in chronic disease prevention.According to the American Institute for Cancer Research, isoflavones mayinhibit enzymes necessary for the growth and the spread of many types ofcancer such as breast cancer, prostate cancer and colon cancer.Isoflavones also have shown great promise in preventing osteoporosis andtreating menopausal symptoms.

[0016] Soybeans contain about 0.5% by weight saponins. Soy saponins havebeen the subject of investigation since the early 20^(th) century. Thesecompounds consist of a triterpenoid skeleton with various sugar andacetyl moieties. The current consensus is that soyasapogenols A, B and Eare true aglycons, while other soyasapogenols are artifacts ofhydrolysis conditions. The corresponding glycosides are the so-called‘group A saponins’, ‘group B saponins’, and ‘group E saponins’,respectively.

[0017] Soy saponins have demonstrated anti-mutagenic properties thatmake them promising agents for cancer prophylaxis. Moreover, group B soysaponins have exhibited pronounced suppressive effects on thereplication in vitro of the human immunodeficiency virus (HIV). Thechemical structure of soybean saponins is very similar to that of thecompound glycyrrhizin, a known anti-viral agent, so soy saponins showpromise as building blocks for the synthesis of anti-viralpharmaceutical compounds.

SUMMARY OF THE INVENTION

[0018] The present invention comprises a soy protein concentrate havinglow oligosaccharide and high isoflavone and saponin content. Morespecifically, the present invention comprises a method, using soy flouror soy flakes as a starting material, for producing soy proteinconcentrate having low non-digestible oligosaccharides and highisoflavone and saponin content.

[0019] It is an objective of the present invention to produce soyprotein concentrates having a protein content of more than 70 wt. % andless than 90 wt. % of total dry matter, and an isoflavone content of atleast 2 milligrams/gram (mg/g) of total dry matter.

[0020] It is another objective of the present invention to produce soyprotein concentrates containing a combined raffinose and stachyosecontent of less than about 50 mg/g of total dry matter.

[0021] It is a further objective of the present invention to produce soyprotein concentrates having a soyasapogenol content of more than 2.0mg/g of total dry matter.

[0022] It is yet a further objective of the present invention to producesoy protein concentrates having a high Nitrogen Solubility Index (NSI).

[0023] In one embodiment, the present invention provides a method formanufacturing a soy protein concentrate that comprises the steps of: (a)providing a defatted soybean material, (b) adding water to the materialto form a slurry, (c) removing fiber from the slurry to produce asuspension, and (d) ultrafiltering the suspension using a membranehaving a molecular weight cutoff (MWCO) of up to 30,000. Perferrably, amembrane having a MWCO of between 10,000 and 30,000 is used.Alternatively, a membrane having a MWCO of 1,000,000 may be used toremove oligosaccharides and to produce a product having a proteincontent of at least 70 wt. % of total dry matter and an isoflavonecontent of at least 2 mg/g of total dry matter.

[0024] The defatted soybean material may be soy flakes or soy flour. Thedefatted material may contain less than about 1.0 wt. % fat, at least 45wt. % protein and have a protein dispersibility index (PDI) of about 90.The defatted material may further contain about 30 to 40 wt. %carbohydrates, and about 5 to 10 wt. % moisture.

[0025] In one specific form of the present invention, an amount of wateris added to the defatted material to produce a slurry that containsabout 5 to 15 wt. % solids.

[0026] In another specific form of the present invention, a membranehaving a molecular weight cutoff of 10,000 is used in the step ofultrafiltering the suspension.

[0027] In one specific embodiment, the method for manufacturing a soyprotein concentrate further comprises the step of recovering a producthaving a protein content of at least 70% of total dry matter and anisoflavone content of at least 2 mg/g of total dry matter. The productfurther contains a combined raffinose and stachyose content of less than50 mg/g of total dry matter.

[0028] In another embodiment of the present invention, the method formanufacturing a soy protein concentrate includes a step of adjusting thepH of the slurry to at least about 7.0, prior to the step of removingthe fiber. Specifically, the pH of the slurry can be adjusted to betweenabout 7 to about 7.5. More specifically, the pH of the slurry isadjusted by adding sodium hydroxide to the slurry.

[0029] In another specific embodiment, the method for manufacturing asoy protein concentrate further comprises a step of spray drying theproduct.

[0030] In yet another specific embodiment, the method for manufacturinga soy protein concentrate further comprises a step of pasteurizing theproduct prior to spray drying the product. The step of pasteurizing theproduct may be accomplished by jet cooking at a temperature of betweenabout 76° C. and about 130° C.; preferably a temperature of above about93° C. is used.

[0031] In another specific embodiment, the method for manufacturing asoy protein concentrate further comprises a step of pasteurizing thesuspension prior to the ultrafiltration step.

[0032] In a more specific embodiment of the present invention, themethod for manufacturing a soy protein concentrate comprises the stepsof (a) providing a defatted soybean material, (b) adding water to thematerial to form a slurry, wherein the slurry has between about 5 and 15wt. % solids, (c) adjusting the pH of the slurry to about 7 to 7.5 withsodium hydroxide, (d) removing fiber from the slurry by centrifugationto produce a suspension, (e) pasteurizing the suspension by jet cookingabove the 115° C., (f) ultrafiltering the suspension using a membranehaving a molecular weight cutoff (MWCO) of up to 30,000 to produce aretentate, (g) pasteurizing the retentate by jet cooking above about 93°C., (h) spray drying the pasteurized retentate to form a product, and(i) recovering the product having a protein content of at least 70 wt. %of total dry matter and at least 2 mg of isoflavones per g of total drymatter.

[0033] In a specific embodiment of the invention, the soy proteinconcentrate comprises a protein content of at least 70 wt. % of totaldry matter and isoflavones of at least 2 mg/g of total dry matter. Thesoy protein concentrate may further comprise a combined raffinose andstachyose content of less than 50 mg/g of total dry matter. The soyprotein concentrate may further comprise a crude fiber of less than 3wt. % of dry matter. Further, the soy protein concentrate may comprise asoyasapogenol content of more than about 2.0 mg/g of total dry matter.

DETAILED DESCRIPTION

[0034] The present method generally encompasses: 1) dehulling wholesoybeans; 2) flaking the dehulled soybeans; 3) extracting soybean oilfrom the flaked soybeans with a solvent; such as hexane; 4)desolventizing the defatted soybean flakes without high heating ortoasting to produce “white” flakes; 5) grinding the flakes to make soyflour; 6) removing fiber from the soy flour and retaining proteins; and7) ultrafiltering to remove carbohydrates and minerals.

[0035] Steps 1 through 4 described above are commonly referred to as theextraction process for soybeans. The general procedure for theabove-described steps 1 through 5 is well understood. See U.S. Pat. No.5,097,017 to Konwinski and U.S. Pat. No. 3,897,574 to Pass, eachassigned to the assignee of the present invention, the disclosures ofwhich are expressly incorporated herein by reference. See also“Extraction of Oil from Soybeans,” J. Am. Oil Chem. Soc., 58, 157 (1981)and “Solvent Extraction of Soybeans,” J. Am. Oil Chem. Soc., 55, 754(1978).

[0036] The first step described above is dehulling. Dehulling is theprocess in which the soybean hulls are removed from the whole soybeans.The soybeans are carefully cleaned prior to dehulling to remove foreignmatter, so that the final product will not be contaminated by colorbodies. Soybeans also are normally cracked into about 6 to 8 piecesprior to dehulling. The hull typically accounts for about 8% of theweight of the whole soybean. The dehulled soybean is about 10% water,40% protein, 20% fat, with the remainder mainly being carbohydrates,fiber and minerals.

[0037] The second step described above is the flaking process. Soybeansare conditioned prior to flaking by adjusting moisture and temperatureto make the soybean pieces sufficiently plastic. The conditioned soybeanpieces are passed through flaking rolls to form flakes of about 0.25 to0.30 millimeters (mm) thick.

[0038] The third step described above involves removal of soybean oilfrom the flakes or defatting. This process is performed by contactingthe flakes with hexane. The oil that is removed by this process may beused in margarine, shortening and other food products. The soybean oilis also a good source of lecithin, which has many useful applications asan emulsifier.

[0039] In the fourth step described above, the hexane-defatted soybeanflakes are desolventized to remove hexane, without toasting, to producewhite flakes. This is different than conventional soybean oil hexaneprocesses where the flakes are toasted and used for animal feed.

[0040] In the fifth step described above, the white flakes are ground tomake soy flour. Soy flour that can be used as a starting material forthe subject invention is readily, commercially available. Commercial soyflour typically would have at least 50% (52.5%) protein (N×6.25); about30-40% (34.6%) carbohydrates; about 5-10% (6%) moisture; about 5-10%(6%) ash; about 2-3% (2.5%) crude fiber; and less than about 1% (0.9%)fat (ether extract).

[0041] The soy flour may have a protein dispersibility index (PDI) of90. PDI is determined by American Oil Chemist's Society (AOCS) method Ba10-65. Soy flour having 90 PDI would be soy flour with no heat treatmentand is enzyme active. The soy flour may be 80 mesh, which means thatmore than 95 wt. % of the soy flour passes through a number 80 mesh USAstandard sieve.

[0042] According to one embodiment of the present invention, thestarting material, which can be soy flour or soy flakes, is producedaccording to the process such as that described in steps 1-5 above.

[0043] The next step involves removing fiber from the starting material.In this step, an amount of water is added to the starting material toform a slurry. The water may be pre-heated to about 50° C. to about 65°C. In a specific embodiment, the slurry contains about 5-15 wt. %solids. It usually is necessary to provide some agitation or mixing toslurry the starting material. One means for performing the mixing is apropeller-type agitator.

[0044] In the step of fiber removal, the pH of the slurry is adjusted toabout 7-7.5, and more preferably about 7.4. The pH may be adjusted byadding sodium hydroxide to the slurry.

[0045] The separation of fiber from the slurry can be performed by anyone of a number of physical separation means, such as by centrifugationusing a decanting centrifuge, for example. After the centrifugation, thecake containing fiber is separated from the suspension, which iscollected.

[0046] In one embodiment of this invention, the suspension ispasteurized. One means for pasteurization is jet cooking at a hightemperature, preferably, at a temperature of about 93° C. Thetemperature may reach about 127° C. In yet another embodiment of thisinvention, the suspension may be pasteurized in a steam-jacketed kettle.

[0047] In the next step, the suspension is ultrafiltered to removeoligosaccharides and other sugars while retaining isoflavones andsaponins in the retentate. Isoflavones and saponins are small molecularweight components, less than 1500 in molecular weight. Surprisingly,however, it has been found that isoflavones and saponins are retained bythe ultafilration membranes in the retentate. It is believed at thistime that the isoflavones and saponins might complex with the proteinssuch that the majority of the isoflavones and saponins are retained inthe retentate. Typically, about 75 wt. % of the feed volume is removedas permeate during the ultrafiltration, resulting in a retentate producthaving a protein content of at least about 70 wt. % of total dry matter.Preferably, the product contains protein at about 75 to 85 wt. % oftotal dry matter.

[0048] Any membrane including spiral-wound membranes with a MWCO of upto 30,000 is suitable for the ultrafiltration step. Preferably, amembrane with a MWCO of between 10,000 and 30,000 is used.Alternatively, a membrane with a MWCO of 1,000,000 may be used.Spiral-wound membranes of different MWCO are commercially and readilyavailable. Suitable membranes are available from, for example, KochMembrane Systems, Wilmington, Mass.; Osmonics, Minnetonka, Minn.; PTIAdvanced Filtration, Oxnard, Calif.; and Synder Filtration, Vacaville,Calif.

[0049] During the ultrafiltration step, the temperature of thesuspension can be lowered. One means of lowering the temperature is toinclude a heat exchanger in the ultrafiltration system and pass coldwater through the heat exchanger. The heat exchanger may be installedprior to or after a pre-filter for the membrane system or within themembrane system itself.

[0050] The ultrafiltered product may be pasteurized before being dried.One means for pasteurization is jet cooking. In yet another embodimentof this invention, the product may be pasteurized in a steam-jacketedkettle. The pasteurization is performed so that the product achieves anacceptable microbial profile and tests negative for salmonella. Thepreferred means of drying is a vertical spray dryer with a high-pressurenozzle.

[0051] The product is dried to form a soy protein concentrate thatcontains isoflavones of at least 2 mg/g of total dry matter. The producthas low non-digestible oligosaccharide content; the combined content ofraffinose and stachyose is less than 50 mg/g of total dry matter. Theproduct may further contain a high content of soyasapogenols, which maybe at least about 2.0 mg/g of total dry matter.

[0052] The product has many uses. For example, it can be used as a milksubstitute and in drink mixes and beverages, such as chocolate, vanillaand pineapple beverages; dairy products, such as fruit yogurt; nutritionand health products, such as protein bars; whole muscle meat injection;surimi products; emulsified meats; cereal products, such as breakfastcereals; bakery products, such as blueberry muffins and other liquid ordry beverage, food or nutritional products. The dried product may becoated with commercial lecithin or other food-grade surfactants, such asmono-diglycerides, to improve water dispersibility and reduce clumpingof the product.

Methods and Standards

[0053] 1. Nitrogen Solubility Index (NSI) was measured according toAmerican Oil Chemists' Method Ba 11-65.

[0054] 2. Protein Dispensability Index (PDI) was measured according toAmerican Oil Chemists' Method Ba 10-65.

[0055] 3. Isoflavones were characterized by the procedure described inThiagarajan, D. G., Bennink, M. R., Bourquin, L. D., and Kavas, F. A.,Prevention of precancerous colonic lesions in rats by soy flakes, soyflour, genistein, and calcium, Am. J. Clin. Nutr. 1998; 68(suppl);1394S-9S.

[0056] 4. Saponins were analyzed using HPLC. An HPLC-based analyticalmethod was developed and validated to estimate saponin precursorspresent in soybean. The method is based on isolation of total saponinsfrom finely ground soybean or soybean products using an ethanolicextraction followed by acid hydrolysis to cleave the conjugated sugarchain(s) to form their aglycons (soyasapogenols). Resultingsoyasapogenols were isolated and concentrated by solid phase extractiontechniques. Soyasapogenols were resolved using a reverse phase columnwith isocratic elusions and detected using an Evaporative LightScattering Detector (ELSD). The quantification of soyasapogenols wasperformed using the calibration curves derived against authenticcompounds. The total soy saponin content is approximately twice thetotal soyasapogenol content (Duhan et al. (2001) Int. J. Food Sci. Nutr.52:53-59).

[0057] The following non-limiting examples are presented to illustratethe invention, which is not to be considered as limited thereto. In theexamples and throughout the specification, percentages are by weightunless otherwise indicated.

EXAMPLE 1

[0058] About 23 kilograms (50 pounds) of soy flour having a proteindispersibility index (PDI) of 86 was dispersed in 236 kilograms (519pounds) of water to form a slurry. The pH was adjusted to about 7.5using sodium hydroxide. The slurry was mixed for 30 minutes at atemperature of about 60° C., and then centrifuged in a decantingcentrifuge. The insoluble centrifuge cake was discarded, and thesupernatant (suspension) was heat treated by passing through a jetcooker at a temperature of about 121° C. with a holding time of 15seconds. The suspension was then cooled to about 48.8° C. in a jacketedvessel. The suspension was then ultrafiltered using a 10,000 molecularweight cutoff (MWCO) spiral-wound membrane to remove about 75 wt. % ofthe feed volume as permeate. The retentate from the membrane was heattreated by passing though a jet cooker at a temperature about 93° C.with a holding time of 15 seconds. The retentate was then cooled toabout 60° C. in a jacketed vessel and spray dried. The product wasanalyzed to determine the content.

[0059] The results from two runs (TABLE 1) show that the product has aprotein content of between 79.79 and 82.97 wt. % of dry matter. Thetotal isoflavone content is more than 2 mg/g of total dry matter and acombined amount of raffinose and stachyose is less than 3 wt. %. Inaddition, the NSI of the product was greater than 95% in both runs.TABLE 1 Composition of product derived from the method of EXAMPLE 1 wt.% Composition Run 1 Run 2 Protein 79.79* 82.97* Moisture 1.23 3.73 Ash(as is) 6.87 6.50 Crude fiber (as is) 0.80 0.80 Monosaccharides (as is)0.13 0.06 Sucrose (as is) 2.88 3.49 Melibiose (as is) 0.00 0.44Raffinose (as is) 0.18 0.32 Stachyose (as is) 1.80 2.40 TotalIsoflavones 2.18** 3.51** Nitrogen Solubility Index (NSI) 96.99 95.45

EXAMPLE 2

[0060] About 227 liters (60 gallons) of water were added to a mixingtank and heated to 60° C. Then, about 45 kilograms (100 pounds) of soyflakes were added to the mixing tank to form a slurry. The pH of theslurry was adjusted to about 7.1, using about 1400 ml of 4.5% NaOHsolution. The slurry was mixed for 10 minutes at a temperature of about550 to about 58° C. and then transferred to a centrifuge feed tank,which contained about 303 liters (80 gallons) of water preheated to atemperature of about 60° C. The diluted slurry was mixed for about 20minutes at a temperature of about 55° to about 58° C. and thereafter fedat a rate of about 7.6 liters (2 gallons) per minute to a Sharplesscroll-type centrifuge. The supernatant (suspension) was jet cooked at atemperature of about 127° C. The jet-cooked suspension was transferredto a membrane feed tank through a 100-mesh strainer. About 10 grams ofsodium metabisulfite was added to the membrane feed tank. The suspensionwas fed to an ultrafiltration membrane system containing a spiral-woundmembrane with a MWCO of 10,000. The temperature of the suspension wasmaintained at about 26.5°-26.8° C. during membrane processing. About 75%of the original feed volume added to the membrane feed tank was removedas permeate. The retentate from the membrane system was pasteurized atabout 76.7° C. and spray dried using a high-pressure pump feeding aspray nozzle in a vertical spray dryer. The dried product was analyzedto determine the content thereof. The results of the analysis are shownin TABLE 2. TABLE 2 Composition of product derived from the method ofEXAMPLE 2 mg/g Composition wt. % of total dry matter protein 82.73 crudefiber 0.94 crude fat 0.01 ash 5.91 fructose 2.90 galactose 1.33 sucrose40.29 raffinose 6.88 stachyose 30.13 isoflavones 4.54 daidzin 0.77glycitin 0.22 genistin 1.00 6″-O-malonyldaidzin 0.916″-O-malonylglycitin 0.16 6″-O-acetyl genistin 0.12 6″-O-malonylgenistin1.24 daidzein 0.05 genistein 0.07 soyasapogenols 4.06 soyasapogenol A1.25 soyasapogenol B 2.81 Nitrogen Solubility Index (NSI) 92

EXAMPLE 3

[0061] About 227 liters (60 gallons) of water were added to a mixingtank and heated to a temperature of about 60° C. Then, about 45kilograms (100 pounds) of soy white flakes were added to the mixing tankto form a slurry. The pH of the slurry was adjusted to about 7.08, usingabout 1400 ml of 4.5% NaOH solution. The slurry was mixed for 10 minutesat a temperature of about 550 to about 58° C. and then transferred to acentrifuge feed tank, which contained about 303 liters (80 gallons) ofwater preheated to a temperature of about 60° C. The diluted slurry wasmixed for about 20 minutes at a temperature of about 550 to about 58° C.and thereafter fed at a rate of about 7.6 liters (2 gallons) per minuteto a Sharples scroll-type centrifuge. The supernatant (suspension) wasjet cooked at a temperature of about 127° C. The jet-cooked suspensionwas transferred to a membrane feed tank through a 100-mesh strainer. Thesuspension was fed to an ultrafiltration membrane system containing aspiral-wound membrane with a MWCO of 10,000. The temperature of thesuspension was maintained at about 48.8° to about 49° C. during membraneprocessing. About 75% of the original feed volume added to the membranefeed tank was removed as permeate. The retentate from the membranesystem was pasteurized at a temperature of about 76.7° C. and spraydried using a high-pressure pump feeding a spray nozzle in a verticalspray dryer. The dried product was analyzed to determine the contentthereof. The results of the analysis are shown in TABLE 3. TABLE 3Composition of product derived from the method of EXAMPLE 3 mg/gComposition wt. % of total dry matter protein 82.81 crude fiber 0.84crude fat 0.13 ash 6.00 fructose 2.72 galactose 1.21 sucrose 30.11raffinose 4.99 stachyose 21.80 isoflavones 3.54 daidzin 0.67 glycitin0.09 genistin 0.90 6″-O-malonyldaidzin 0.61 6″-O-malonylglycitin 0.086″-O-acetyl genistin 0.16 6″-O-malonylgenistin 0.96 daidzein 0.03genistein 0.04 soyasapogenols 3.98 soyasapogenol A 1.05 soyasapogenol B2.93 Nitrogen Solubility Index (NSI) 93.8

EXAMPLE 4

[0062] About 227 liters (60 gallons) of water were added to a mixingtank and heated to a temperature of about 60° C. Then, about 45kilograms (100 pounds) of soy flour were added to the mixing tank toform a slurry. The pH of the slurry was adjusted to about 7.08, usingabout 1400 ml of 4.5% NaOH solution. The slurry was mixed for 10 minutesat a temperature of about 55° to about 58° C. and then transferred to acentrifuge feed tank, which contained about 303 liters (80 gallons) ofwater preheated to a temperature of about 60° C. The diluted slurry wasmixed for about 20 minutes at a temperature of about 55° to about 58° C.and thereafter fed at a rate of about 7.6 liters (2 gallons) per minuteto a Sharples scroll-type centrifuge. The supernatant (suspension) wasjet cooked at a temperature of about 127° C. The jet-cooked suspensionwas transferred to a membrane feed tank through a 100-mesh strainer. Thesuspension was fed to an ultrafiltration membrane system containing aspiral-wound membrane with a MWCO of 30,000. The temperature of thesuspension was maintained at about 48.8° to about 49° C. during membraneprocessing. About 75% of the original feed volume added to the membranefeed tank was removed as permeate. The retentate from the membranesystem was pasteurized at a temperature of about 76.7° C. and spraydried using a high-pressure pump feeding a spray nozzle in a verticalspray dryer. The dried product was analyzed to determine the contentthereof. The results of the analysis are shown in TABLE 4. TABLE 4Composition of product derived from the method of EXAMPLE 4 mg/gComposition wt. % of total dry matter protein 82.31 crude fiber 1.14crude fat 0.01 ash 5.44 fructose 2.79 galactose 1.60 sucrose 33.14raffinose 5.88 stachyose 24.24 isoflavones 3.53 daidzin 0.60 glycitin0.17 genistin 0.70 6″-O-malonyldaidzin 0.76 6″-O-malonylglycitin 0.116″-O-acetyl genistin 0.09 6″-O-malonylgenistin 0.99 daidzein 0.04genistein 0.07 soyasapogenols 3.74 soyasapogenol A 1.04 soyasapogenol B2.70 Nitrogen Solubility Index (NSI) 89.2

EXAMPLE 5

[0063] About 227 liters (60 gallons) of water were added to a mixingtank and heated to a temperature of about 60° C. Then, about 45kilograms (100 pounds) of soy flour were added to the mixing tank toform a slurry. The pH of the slurry was adjusted to about 7.0, usingabout 1400 ml of 4.5% NaOH solution. The slurry was mixed for 10 minutesat a temperature of about 550 to about 58° C. and then transferred to acentrifuge feed tank, which contained about 303 liters (80 gallons) ofwater preheated to a temperature of about 60° C. The diluted slurry wasmixed for about 20 minutes at a temperature of about 55° to about 58° C.and thereafter fed at a rate of about 7.6 liters (2 gallons) per minuteto a Sharples scroll-type centrifuge. The supernatant (suspension) wasjet cooked at a temperature of about 127° C. The jet-cooked suspensionwas transferred to a membrane feed tank through a 100-mesh strainer. Thesuspension was fed to an ultrafiltration membrane system containing aspiral-wound membrane with a MWCO of 1,000,000. The temperature of thesuspension was maintained at about 48.8° to about 49° C. during membraneprocessing. About 75% of the original feed volume added to the membranefeed tank was removed as permeate. The retentate from the membranesystem was pasteurized at a temperature of about 76.7° C. and spraydried using a high-pressure pump feeding a spray nozzle in a verticalspray dryer. The dried product was analyzed to determine the contentthereof. The results of the analysis are shown in TABLE 5. TABLE 5Composition of product derived from the method of EXAMPLE 5 mg/gComposition wt. % of total dry matter protein 82.32 crude fiber 1.25crude fat 0.07 ash 5.72 fructose 2.78 galactose 1.38 sucrose 36.44raffinose 6.82 stachyose 26.07 isoflavones 3.37 daidzin 0.54 glycitin0.16 genistin 0.69 6″-O-malonyldaidzin 0.74 6″-O-malonylglycitin 0.116″-O-acetyl genistin 0.10 6″-O-malonylgenistin 0.98 daidzein 0.02genistein 0.03 soyasapogenols 3.55 soyasapogenol A 1.04 soyasapogenol B2.51 Nitrogen Solubility Index (NSI) 90.7

What is claimed is:
 1. A method for manufacturing a soy proteinconcentrate comprising the steps of: (a) providing a substantiallydefatted soybean material; (b) adding water to said material to form aslurry; (c) removing fiber from said slurry to produce a suspension; and(d) ultrafiltering said suspension using a membrane having a molecularweight cutoff of up to 30,000 to reduce the amount of oligosaccharidesand to produce a product having a protein content of at least 70 wt. %of total dry matter and an isoflavone content of at least 2 mg/g oftotal dry matter.
 2. The method of claim 1, wherein said defattedsoybean material contains less than about 1 wt. % fat, and has a proteindispersibility index of about
 90. 3. The method of claim 2, wherein saiddefatted soybean material further contains about 30 to 40 wt. %carbohydrates and about 5 to 10 wt. % moisture.
 4. The method of claim1, wherein said slurry contains about 5 to 15 wt. % solids.
 5. Themethod of claim 1, wherein said membrane has a molecular weight cutoffof between 10,000 and 30,000.
 6. The method of claim 1, wherein saidproduct contains crude fiber less than about 3 wt. % of total drymatter.
 7. The method of claim 1, wherein said product contains lessthan 40 mg of combined raffinose and stachyose per gram of total drymatter.
 8. The method of claim 1, wherein said product contains lessthan about 50 mg of combined raffinose and stachyose per gram of totaldry matter.
 9. The method of claim 1, wherein said product contains morethan about 2.0 mg of soyasapogenols per gram of total dry matter. 10.The method of claim 1 further comprising the step of adjusting the pH ofsaid slurry to at least about 7.0, prior to the step (c).
 11. The methodof claim 10, wherein the pH of said slurry is adjusted to between about7 to about 7.5.
 12. The method of claim 10, wherein the pH of saidslurry is adjusted by adding sodium hydroxide to said slurry.
 13. Themethod of claim 1 further comprising a step of centrifuging said slurryto separate a cake containing a high amount of fiber from saidsuspension.
 14. The method of claim 1 further comprising a step of spraydrying said product.
 15. The method of claim 1 further comprising thesteps of pasteurizing said product and spray drying said product. 16.The method of claim 15, wherein the step of pasteurizing said product isaccomplished by jet cooking at a temperature above about 93° C.
 17. Themethod of claim 16 further comprising a step of pasteurizing saidsuspension prior to said ultrafiltration step.
 18. The method of claim1, wherein said substantially defatted soybean material comprises atleast one of soy flakes and soy flour.
 19. A method for manufacturing asoy protein concentrate comprising the steps of (a) providing a defattedsoybean material; (b) adding water to said material to form a slurryhaving about 5 and 15% solids; (c) adjusting the pH of said slurry toabout 7 to 7.5 with sodium hydroxide; (d) removing fiber from saidslurry by centrifugation to produce a suspension; (e) pasteurizing saidsuspension; (f) ultrafiltering said suspension using a membrane having amolecular weight cutoff of up to 30,000 to produce a retentate; (h)pasteurizing said retentate by jet cooking at a temperature above about93° C.; (i) spray drying said retentate to form a product; and (j)recovering said product having a protein content of at least 70 wt. % oftotal dry matter and at least 2 mg of isoflavones per g of total drymatter.
 20. A soy protein concentrate comprising a protein content of atleast 70 wt. % of total dry matter, at least 2 mg of isoflavones per gof total dry matter, and less than 3 wt. % crude fiber of total drymatter.
 21. The soy protein concentrate of claim 20 further comprising acombined raffinose and stachyose content of less than 50 mg/g of totaldry matter.
 22. The soy protein concentrate of claim 20 furthercomprising a Nitrogen Solubility Index (NSI) of greater than 80%. 23.The soy protein concentrate of claim 20 further comprising crude fiberof less than 2 wt. % of total dry matter.
 24. The soy proteinconcentrate of claim 20, wherein the protein content is between 75 wt. %and 85 wt. % of total dry matter.
 25. The soy protein concentrate ofclaim 20, wherein soyasapogenols contents is more that about 2.0 mg/g oftotal dry matter.
 26. A food product comprising the soy proteinconcentrate made by the method of claim
 20. 27. The food product ofclaim 26 comprising a liquid beverage.
 28. The food product of claim 26comprising a dry form of a beverage.
 29. A method for manufacturing asoy protein concentrate comprising the steps of: (a) providing adefatted soybean material; (b) adding water to said material to form aslurry; (c) removing fiber from said slurry to produce a suspension; and(d) ultrafiltering said suspension using a membrane having a molecularweight cutoff of 1,000,000 to remove non-digestible oligosaccharides andto produce a product having a protein content of at least 70 wt. % oftotal dry matter and an isoflavone content of at least 2 mg/g of totaldry matter.
 30. The method of claim 29, wherein the product containsmore than about 2.0 mg of soyasapogenols per g of total dry matter. 31.A food product comprising the soy protein concentrate made by the methodof claim
 1. 32. A food product comprising the soy protein concentratemade by the method of claim
 19. 33. A food product comprising the soyprotein concentrate made by the method of claim 29.